A universal mobile telecommunications system (UMTS) is a third-generation mobile communications system that evolved from a global system for mobile communications system (GSM). The UMTS is intended to provide enhanced mobile communications services based on the GSM core network and wideband code-division multiple-access (WCDMA) technology. The UMTS terrestrial radio access network (UTRAN) is a radio access network for supporting WCDMA access technology in the UMTS.
Typically, the interface between a user equipment (UE) and the UTRAN has been realized in the related art through a radio interface protocol established in accordance with radio access network specifications describing a physical layer (L1), a data link layer (L2) and a network layer (L3). These layers are based on the lower three layers of an open system interconnection (OSI) model that is well known in communications systems.
For example, the physical layer (PHY) provides information transfer service to a higher layer and is linked via transport channels to a medium access control (MAC) layer. Data travels between the MAC layer at L2 and the physical layer at L1, via a transport channel. The transport channel is divided into a dedicated transport channel and a common transport channel depending on whether a channel is shared. Also, data transmission is performed through a physical channel between different physical layers, namely, between physical layers of a sending side (transmitter) and a receiving side (receiver).
In this example of a typical system in the related art, the second layer L2 includes the MAC layer, a radio link control (RLC) layer, a broadcast/multicast control (BMC) layer, and a packet data convergence protocol (PDCP) layer. The MAC layer maps various logical channels to various transport channels. The MAC layer also multiplexes logical channels by mapping several logical channels to one transport channel. The MAC layer is connected to an upper RLC layer via the logical channel. The logical channel can be divided into a control channel for transmitting control plane information, and a traffic channel for transmitting user plane information according to the type of information transmitted. The term “traffic” can sometimes be understood to cover control information, but in this present specification the term “traffic signal” will refer to a data signal in the user plane.
The MAC layer within L2 is divided into a MAC-b sublayer, a MAC-d sublayer, a MAC-c/sh sublayer, a MAC-hs sublayer and a MAC-e sublayer according to the type of transport channel being managed. The MAC-b sublayer manages a broadcast channel (BCH), which is a transport channel handling the broadcast of system information. The MAC-c/sh sublayer manages common transport channels such as an FACH (Forward Access Channel) or a DSCH (Downlink Shared Channel) that is shared by other terminals. The MAC-d sublayer handles the managing of a DCH (Dedicated Channel), namely, a dedicated transport channel for a specific terminal. In order to support uplink and downlink high speed data transmissions, the MAC-hs sublayer manages an HS-DSCH (High Speed Downlink Shared Channel), namely, a transport channel for high speed downlink data transmission, and the MAC-e sublayer manages an E-DCH (Enhanced Dedicated Channel), namely, a transport channel for high speed uplink data transmissions.
In this example of a typical related art system, a radio resource control (RRC) layer located at the lowest portion of the third layer (L3) controls the parameters of the first and second layers with respect to the establishment, reconfiguration and release of radio bearers (RBs). The RRC layer also controls logical channels, transport channels and physical channels. Here, the RB refers to a logical path provided by the first and second layers of the radio protocol for data transmission between the terminal and the UTRAN. In general, the establishment of the RB refers to stipulating the characteristics of a protocol layer and a channel required for providing a specific data service, and setting their respective detailed parameters and operation methods.
A typical HSUPA (High Speed Uplink Packet Access) of the related art will now be briefly described. HSUPA is a system allowing a terminal or UE to transmit data to the UTRAN via the uplink at a high speed. The HSUPA employs an enhanced dedicated channel (E-DCH), instead of the related art dedicated channel (DCH), and also uses a HARQ (Hybrid Automatic Repeat Request) and AMC (Adaptive Modulation and Coding), required for high-speed transmissions, and a technique such as a Node B-controlled scheduling. For the HSUPA, the Node B transmits to the terminal downlink control information for controlling the E-DCH transmission of the terminal. The downlink control information includes response information (ACK/NACK) for the HARQ, channel quality information for the AMC, E-DCH transmission rate allocation information for the Node B-controlled scheduling, E-DCH transmission start time and transmission time interval allocation information, transport block size information, and the like. The terminal transmits uplink control information to the Node B. The uplink control information includes E-DCH transmission rate request information for Node B-controlled scheduling, UE buffer status information, UE power status information, and the like. The uplink and downlink control information for the HSUPA are transmitted via physical control channels such as an E-DPCCH (Enhanced Dedicated Physical Control Channel) in the uplink and E-HICH (HARQ acknowledgement Indication channel), E-RGCH (Relative Grant channel) and E-AGCH (Absolute Grant channel) in the downlink. For the HSUPA, a MAC-d flow is defined between the MAC-d and MAC-e. Here, a dedicated logical channel such as a DCCH (Dedicated Control Channel) or a DTCH (Dedicated Traffic Channel) is mapped to the MAC-d flow. The MAC-d flow is mapped to the transport channel E-DCH and the transport channel E-DCH is mapped to the physical channel E-DPDCH (Enhanced Dedicated Physical Data Channel). The dedicated logical channel can also be directly mapped to the transport channel DCH. In this case, the DCH is mapped to the physical channel DPDCH (Dedicated Physical Data Channel).
According to Wideband Code Division Multiple Access (WCDMA) standards, the uplink (UL) Dedicated Physical Control Channel (DPCCH) carries control information generated at layer 1, which is the physical layer (PHY). The layer 1 control information consists, for example, of known pilot bits to support channel estimation for coherent detection, transmit power control (TPC) for the downlink (DL) dedicated physical channel (DPCH), feedback information (FBI), and an optional transport format combination indicator (TFCI). Uplink (UL) DPCCH is continuously transmitted, and there is one UL DPCCH for each radio link.
When there are many users in a cell, a high capacity is desirable for VoIP on High Speed Downlink Packet Access (HSDPA) and HSUPA, and then the interference caused by continuously transmitted UL DPCCHs becomes a limiting factor for capacity. It would therefore be desirable to improve the capacity for VoIP by revising the limiting factor.
Data traffic (e.g. VoIP) is transmitted on an Enhanced Dedicated Channel (E-DCH), which is transmitted on an Enhanced Dedicated Physical Data Channel (E-DPDCH). Control signaling associated with E-DPDCH is transmitted on an Enhanced Dedicated Physical Control Channel (E-DPCCH). These channels are transmitted only when there is data to be transmitted and when the transmission has been granted by the network, i.e., these transmissions are discontinuous. The Dedicated Physical Control Channel (DPCCH) is a dedicated control channel which carries pilot bits for channel and signal to interference ratio (SIR) estimation purposes, and it also carries power control bits for DL DPCH, as well as TFCI bits indicating transport format used on DPDCH, and FBI bits carrying feedback information from User Equipment UE to base station Node B (TFCI and FBI bits are, however, not needed if E-DPDCH is used); this transmission is continuous, even if there is no data to transmit for a while, and this is acceptable with circuit switched services which typically send continuously. However, for bursty packet services, continuous DPCCH transmission causes quite a big overhead.
It is known in the art to use UL DPCCH gating in the context of the “Terminal power saving feature.” See, for example, section 8.1.2 of 3GPP TR 25.840, V4.0.0 (2003-12), “Terminal Power Saving Features.” However, the full capabilities of UL DPCCH gating have not yet been exploited with HSUPA transmissions.
DPCCH gating involves breaks in the DPCCH transmission or DTX, which is a discontinuous transmission using the DPCCH. Generally speaking, DTX is a battery-saving feature that cuts back the output power when a person stops speaking. DPCCH gating is known, at least for power saving purposes. Earlier, some regular (or pseudo-random) DTX patterns have been considered. However, UL DPCCH gating has thus far not been fully exploited in the context of HSDPA and HSUPA transmissions.